3 Blades vs 5 Blades

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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #62
    Re: 3 Blades vs 5 Blades

    not even long enough to get your first electric bill
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  • lucymarco
    lucymarco Registered Users, Users Awaiting Email Confirmation Posts: 1 ✭
    #63
    I'm a middle school student and i'm working on a project about wind turbines my hypothesis was if 3, 6 and 8 blades put on a wind turbine 3 blades will produce the most electricity. but my results show that 6 blades was the best and 3 blades was the worst. I didn't find any reason why? 
    now I should write my conclusion that why 6 blades was better the 3 blades and I should give a  reason why? I don't know what to do. do you have any suggestion for me to write in my conclusion?
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited December 2017 #64
    There difference between a 3 blade and 6 blade is, the 3 blade can operate at higher speeds before the blades begin entering the wake of the other blades, which is favorable for electrical generation. However a turbine is used for direct power, such as  pumping water, where speed is not as important as torque, more blades such as 6, will be benificial because speed is not a requirement, therefore blade turbulence is less of an issue. See link for more information 
    https://www.quora.com/Why-is-3-the-optimal-number-of-blades-on-a-wind-turbine-instead-of-say-5-or-more
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
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  • BilljustBill
    BilljustBill Solar Expert Posts: 219 ✭✭✭
    #65
    bmet said:
    Re: 3 Blades vs 5 Blades

    not even long enough to get your first electric bill

    lucymarco said:
    I'm a middle school student and i'm working on a project about wind turbines my hypothesis was if 3, 6 and 8 blades put on a wind turbine 3 blades will produce the most electricity. but my results show that 6 blades was the best and 3 blades was the worst. I didn't find any reason why? 
    now I should write my conclusion that why 6 blades was better the 3 blades and I should give a  reason why? I don't know what to do. do you have any suggestion for me to write in my conclusion?


    It may be that the generator you are using reaches its threshold to begin producing enough "Charging Power" at a lower RPM and doesn't need the speed.  So, the three blade rotor may not grab the low speed air as well as your 6-blade rotor, therefore more low speed wind slips by the 3-blade rotor than spins it.

    Use this link and go asked the maker/seller of various small size wind generators why he sells wind generators that have 3 to 9 blades making up his brands/models of blade rotors.  If you find out, please post back here and tell what/why he sells so many variations of in the number of blades for his Win-Gens.

    https://www.ebay.com/itm/DC-output-Confederate-3-blade-500-watt-12-volt-wind-turbine-turbulent-wind/292049663027?hash=item43ff843433:g:cG4AAOSw2gxYwGRO

    Learn by Doing is a great way to understand and remember how and why things work.... ;>)

    Bill

    Bill
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #66
    john p said:
    Re: 3 Blades vs 5 Blades

    im running an Air x now with 5 blades. 5ft dia as against the 3 blade 4feet dia
    it definately is less noisy than when it had 3 blades. the manufacturer of the 5 blade set says its because the "holes " between the blades are smaller.. I have no idea except it makes a lot less noise
    The generator starts making power in much lower winds than when using 3 blades
    its production of power is much greater in high winds,
    it was producing so much power in high winds it bent the 2" dia last 3 ft of pipe. had to add guy wires.

    I suspect all of that is due to the larger diameter of the rotor.  A 5 ft dia rotor will produce 50% more power than a 4 ft dia rotor based purely on swept area - and will tend to rotate more slowly (RPM-wise) to maintain the same tip speed.
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  • dperchlik
    dperchlik Registered Users Posts: 1 ✭
    #67
    Very interesting thread.  I would like to point out that higher RPM does NOT equal higher Power.  Higher RPM equals higher Voltage.  If you had a resistive load, higher RPM would result in higher power to the load.  If you have a three phase rectifier and a PWM converter to give you a fixed voltage or a controlled voltage to charge a battery, the load on the turbine (power provided) would be relative to the current you are drawing. The more power you draw, the more load is seen by the turbine and the RPMs will reduce with the same wind speed.  Run your turbine with no load, it will turn very fast but there is no power, add a dump load and the RPMs and voltage will go down, and there will be significant power dissipated in the dump load.
    If you want to see the math that backs this up Calculations | Simple Electric Motors (simplemotor.com)

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